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Topic Title: Fire alarms
Topic Summary: Correct way ?
Created On: 23 February 2014 11:15 AM
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 23 February 2014 11:15 AM
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Ampman

Posts: 1009
Joined: 06 February 2006

Good morning ,

When im doing a fire alarm system i like make the smoke alarms off by either fitting a circular plaster box with stuffing glands & terminating ,

Or install a galvo box above in floors with glands etc....

But the more & more im seeing no glands etc... cables just pushed into detector , to me this is wrong & rough ,

Or am i wasting time doing a neat job ?

cheers
 23 February 2014 11:37 AM
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weirdbeard

Posts: 1499
Joined: 26 September 2011

Hi ampman, I don't do fire alarms, but stick with what you are doing - it sounds good, don't worry about what others are doing!

Google says that it's as BS7671 thing:

"BSI published a queries and interpretation document at the end of last year, PD 6531:2010, one of the questions asked was -

Query

Do fire cables conforming to BS 7629-1 have to be terminated into fire alarm initiation points (manual call points, automatic fire detection devices, etc.) and fire alarm devices (sounders, etc.) using compression glands?

Answer

BS 5839-1:2002+A2, 37.2, states that the fire alarm system should
conform to the requirements of BS 7671.
BS 7671:2008, 522.8.5, states, "Every cable or conductor shall be
supported in such a way that it is not exposed to undue mechanical
strain and so that there is no appreciable mechanical strain on the
terminations of the conductors, account being taken of mechanical
strain imposed by the supported weight of the cable or conductor
itself."

There are several scenarios that require consideration.
a) Cables in ceiling/floor voids terminating into devices (e.g. smoke
detectors on the room side of a ceiling tile). In this scenario,
cables should be terminated into the device by the use of suitable
conduit boxes and compression glands. If the cables are not
terminated in this way, cables and terminations could be placed
under undue mechanical strain by interference from people
working in the void and moving the cables either deliberately or
inadvertently. Additionally, in a fire situation, the surface to which
the detector is attached might collapse due to fire damage, again
causing undue mechanical strain on the cables and terminations,
which could in turn adversely affect the operation of the fire
detection and alarm system.

b) Cables running vertically to a manual call point. In this case, it
might be possible to exclude the compression gland if the back
box for the manual call point is either too shallow to enable the
use of a compression gland in a flush installation or protective
mini trunking is used in a surface installation.
Glands also serve the purpose of excluding dust, water, insects or any
other item or species. Manufacturers of fire resisting cables recommend
the use of compression glands to terminate cables and therefore
cable installers should check with the relevant manufacturers as to the
effect upon the fire performance of cables when terminated without
compression glands. "

From page 1 of this topic from a fire alarm forum:

http://firealarmengineers.com/...howthread.php?tid=3541
 23 February 2014 01:00 PM
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kirchoffs

Posts: 180
Joined: 08 February 2010

Ampman Carry on doing it your way , i've done it that way since 1974
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